Add Swappy & Pre-Transformed Swapchain

- Adds Swappy for Android for stable frame pacing
- Implements pre-transformed Swapchain so that Godot's compositor is in
charge of rotating the screen instead of Android's compositor
(performance optimization for phones that don't have HW rotator)

============================

The work was performed by collaboration of TheForge and Google. I am
merely splitting it up into smaller PRs and cleaning it up.

Changes from original PR:

- Removed "display/window/frame_pacing/android/target_frame_rate" option
to use Engine::get_max_fps instead.
- Target framerate can be changed at runtime using Engine::set_max_fps.
- Swappy is enabled by default.
- Added documentation.
- enable_auto_swap setting is replaced with swappy_mode.

platform/android/java/lib/src/org/godotengine/godot/GodotIO.java

@@ -47,6 +47,7 @@ import android.util.DisplayMetrics;
 import android.util.Log;
 import android.view.Display;
 import android.view.DisplayCutout;
+import android.view.Surface;
 import android.view.WindowInsets;
 
 import androidx.core.content.FileProvider;
@@ -295,6 +296,28 @@ public class GodotIO {
 		}
 	}
 
+	/**
+	 This function is used by DisplayServer::screen_get_internal_current_rotation (C++)
+		and is used to implement a performance optimization in devices that do not offer
+		a HW rotator.
+	 @return
+		Rotation in degrees, in multiples of 90°
+	*/
+	public int getInternalCurrentScreenRotation() {
+		int rotation = activity.getWindowManager().getDefaultDisplay().getRotation();
+
+		switch (rotation) {
+			case Surface.ROTATION_90:
+				return 90;
+			case Surface.ROTATION_180:
+				return 180;
+			case Surface.ROTATION_270:
+				return 270;
+			default:
+				return 0;
+		}
+	}
+
 	public void setEdit(GodotEditText _edit) {
 		edit = _edit;
 	}